/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_bitreversal.c
*
* Description:	This file has common tables like Bitreverse, reciprocal etc which are used across different functions
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
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*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* -------------------------------------------------------------------- */

#include "arm_math.h"
#include "arm_common_tables.h"

/*
* @brief  In-place bit reversal function.
* @param[in, out] *pSrc        points to the in-place buffer of floating-point data type.
* @param[in]      fftSize      length of the FFT.
* @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.
* @param[in]      *pBitRevTab  points to the bit reversal table.
* @return none.
*/

void arm_bitreversal_f32(
    float32_t *pSrc,
    uint16_t fftSize,
    uint16_t bitRevFactor,
    uint16_t *pBitRevTab)
{
    uint16_t fftLenBy2, fftLenBy2p1;
    uint16_t i, j;
    float32_t in;

    /*  Initializations */
    j = 0u;
    fftLenBy2 = fftSize >> 1u;
    fftLenBy2p1 = (fftSize >> 1u) + 1u;

    /* Bit Reversal Implementation */
    for (i = 0u; i <= (fftLenBy2 - 2u); i += 2u)
    {
        if(i < j)
        {
            /*  pSrc[i] <-> pSrc[j]; */
            in = pSrc[2u * i];
            pSrc[2u * i] = pSrc[2u * j];
            pSrc[2u * j] = in;

            /*  pSrc[i+1u] <-> pSrc[j+1u] */
            in = pSrc[(2u * i) + 1u];
            pSrc[(2u * i) + 1u] = pSrc[(2u * j) + 1u];
            pSrc[(2u * j) + 1u] = in;

            /*  pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
            in = pSrc[2u * (i + fftLenBy2p1)];
            pSrc[2u * (i + fftLenBy2p1)] = pSrc[2u * (j + fftLenBy2p1)];
            pSrc[2u * (j + fftLenBy2p1)] = in;

            /*  pSrc[i+fftLenBy2p1+1u] <-> pSrc[j+fftLenBy2p1+1u] */
            in = pSrc[(2u * (i + fftLenBy2p1)) + 1u];
            pSrc[(2u * (i + fftLenBy2p1)) + 1u] =
                pSrc[(2u * (j + fftLenBy2p1)) + 1u];
            pSrc[(2u * (j + fftLenBy2p1)) + 1u] = in;

        }

        /*  pSrc[i+1u] <-> pSrc[j+1u] */
        in = pSrc[2u * (i + 1u)];
        pSrc[2u * (i + 1u)] = pSrc[2u * (j + fftLenBy2)];
        pSrc[2u * (j + fftLenBy2)] = in;

        /*  pSrc[i+2u] <-> pSrc[j+2u] */
        in = pSrc[(2u * (i + 1u)) + 1u];
        pSrc[(2u * (i + 1u)) + 1u] = pSrc[(2u * (j + fftLenBy2)) + 1u];
        pSrc[(2u * (j + fftLenBy2)) + 1u] = in;

        /*  Reading the index for the bit reversal */
        j = *pBitRevTab;

        /*  Updating the bit reversal index depending on the fft length  */
        pBitRevTab += bitRevFactor;
    }
}



/*
* @brief  In-place bit reversal function.
* @param[in, out] *pSrc        points to the in-place buffer of Q31 data type.
* @param[in]      fftLen       length of the FFT.
* @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
* @param[in]      *pBitRevTab  points to bit reversal table.
* @return none.
*/

void arm_bitreversal_q31(
    q31_t *pSrc,
    uint32_t fftLen,
    uint16_t bitRevFactor,
    uint16_t *pBitRevTable)
{
    uint32_t fftLenBy2, fftLenBy2p1, i, j;
    q31_t in;

    /*  Initializations      */
    j = 0u;
    fftLenBy2 = fftLen / 2u;
    fftLenBy2p1 = (fftLen / 2u) + 1u;

    /* Bit Reversal Implementation */
    for (i = 0u; i <= (fftLenBy2 - 2u); i += 2u)
    {
        if(i < j)
        {
            /*  pSrc[i] <-> pSrc[j]; */
            in = pSrc[2u * i];
            pSrc[2u * i] = pSrc[2u * j];
            pSrc[2u * j] = in;

            /*  pSrc[i+1u] <-> pSrc[j+1u] */
            in = pSrc[(2u * i) + 1u];
            pSrc[(2u * i) + 1u] = pSrc[(2u * j) + 1u];
            pSrc[(2u * j) + 1u] = in;

            /*  pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
            in = pSrc[2u * (i + fftLenBy2p1)];
            pSrc[2u * (i + fftLenBy2p1)] = pSrc[2u * (j + fftLenBy2p1)];
            pSrc[2u * (j + fftLenBy2p1)] = in;

            /*  pSrc[i+fftLenBy2p1+1u] <-> pSrc[j+fftLenBy2p1+1u] */
            in = pSrc[(2u * (i + fftLenBy2p1)) + 1u];
            pSrc[(2u * (i + fftLenBy2p1)) + 1u] =
                pSrc[(2u * (j + fftLenBy2p1)) + 1u];
            pSrc[(2u * (j + fftLenBy2p1)) + 1u] = in;

        }

        /*  pSrc[i+1u] <-> pSrc[j+1u] */
        in = pSrc[2u * (i + 1u)];
        pSrc[2u * (i + 1u)] = pSrc[2u * (j + fftLenBy2)];
        pSrc[2u * (j + fftLenBy2)] = in;

        /*  pSrc[i+2u] <-> pSrc[j+2u] */
        in = pSrc[(2u * (i + 1u)) + 1u];
        pSrc[(2u * (i + 1u)) + 1u] = pSrc[(2u * (j + fftLenBy2)) + 1u];
        pSrc[(2u * (j + fftLenBy2)) + 1u] = in;

        /*  Reading the index for the bit reversal */
        j = *pBitRevTable;

        /*  Updating the bit reversal index depending on the fft length */
        pBitRevTable += bitRevFactor;
    }
}



/*
   * @brief  In-place bit reversal function.
   * @param[in, out] *pSrc        points to the in-place buffer of Q15 data type.
   * @param[in]      fftLen       length of the FFT.
   * @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table
   * @param[in]      *pBitRevTab  points to bit reversal table.
   * @return none.
*/

void arm_bitreversal_q15(
    q15_t *pSrc16,
    uint32_t fftLen,
    uint16_t bitRevFactor,
    uint16_t *pBitRevTab)
{
    q31_t *pSrc = (q31_t *) pSrc16;
    q31_t in;
    uint32_t fftLenBy2, fftLenBy2p1;
    uint32_t i, j;

    /*  Initializations */
    j = 0u;
    fftLenBy2 = fftLen / 2u;
    fftLenBy2p1 = (fftLen / 2u) + 1u;

    /* Bit Reversal Implementation */
    for (i = 0u; i <= (fftLenBy2 - 2u); i += 2u)
    {
        if(i < j)
        {
            /*  pSrc[i] <-> pSrc[j]; */
            /*  pSrc[i+1u] <-> pSrc[j+1u] */
            in = pSrc[i];
            pSrc[i] = pSrc[j];
            pSrc[j] = in;

            /*  pSrc[i + fftLenBy2p1] <-> pSrc[j + fftLenBy2p1];  */
            /*  pSrc[i + fftLenBy2p1+1u] <-> pSrc[j + fftLenBy2p1+1u] */
            in = pSrc[i + fftLenBy2p1];
            pSrc[i + fftLenBy2p1] = pSrc[j + fftLenBy2p1];
            pSrc[j + fftLenBy2p1] = in;
        }

        /*  pSrc[i+1u] <-> pSrc[j+fftLenBy2];         */
        /*  pSrc[i+2] <-> pSrc[j+fftLenBy2+1u]  */
        in = pSrc[i + 1u];
        pSrc[i + 1u] = pSrc[j + fftLenBy2];
        pSrc[j + fftLenBy2] = in;

        /*  Reading the index for the bit reversal */
        j = *pBitRevTab;

        /*  Updating the bit reversal index depending on the fft length  */
        pBitRevTab += bitRevFactor;
    }
}
